Method and apparatus for allowing soft handoff of a CDMA reverse link utilizing an orthogonal channel structure

ABSTRACT

Method and apparatus for base stations and subscriber units allows soft handoff of a CDMA reverse link utilizing an orthogonal channel structure. Subscriber units transmit an orthogonally coded signal over a reverse link to the base stations. A given base station provides timing control of the timing offset of the reverse link signal. Based on at least one criterion, an alignment controller determines that the given base station should hand off timing control to another base station, and a soft handoff process ensues. In response to a command or message for soft handoff of the subscriber unit from the given base station to another base station, the subscriber unit makes a coarse timing adjustment to the timing of the coded signal. The subscriber unit may make fine timing adjustments based on feedback from the base station controlling timing. Multiple base stations may provide power control feedback to the subscriber unit.

RELATED APPLICATION(S)

[0001] This application claims the benefit of U.S. ProvisionalApplication No. 60/427,847, filed on Nov. 20, 2002 entitled “ComponentTechnology Proposal for an Orthogonal Reverse Link”, and is aContinuation-in-Part of U.S. application Ser. No. 09/898,514, filed Jul.3, 2001, entitled “Method for Allowing Multi-User Orthogonal andNon-Orthogonal Interoperability of Code Channels,” which claims priorityto U.S. Provisional Application No. 60/219,789, filed Jul. 19, 2000entitled “Method for Allowing Multi-User Orthogonal and Non-OrthogonalInteroperability of Code Channels on the Reverse Link of a CDMA System.”The entire teachings of the above applications are incorporated hereinby reference.

BACKGROUND OF THE INVENTION

[0002] The last twenty years have seen unprecedented growth in both thetype and demand for wireless communication services. Wireless voicecommunication services, including cellular telephone, PersonalCommunication Services (PCS), and similar systems now provide nearlyubiquitous coverage. The infrastructure for such networks has beenbuilt-out to the point where most residents of the United States,Europe, and other industrialized regions of the world have not just one,but multiple service providers from which to choose.

[0003] Continued growth in the electronics and computer industriesincreasingly contributes to demand for access to the Internet and themyriad of services and features that it provides. This proliferation inthe use of computing equipment, especially that of the portable variety,including laptop computers, handheld Personal Digital Assistants (PDAs),Internet-enabled cellular telephones and like devices, has resulted in acorresponding increase in the need for wireless data access.

[0004] While the cellular telephone and PCS networks are widelydeployed, these systems were not originally intended for carrying datatraffic. Instead, these networks were designed to efficiently supportcontinuous analog signals as compared to the burst mode digitalcommunication protocols needed for Internet communications. Consideralso that voice communication is adequate with a communication channelbandwidth of approximately 3 kilohertz (kHz). However, it is generallyaccepted that for effective Internet communication, such as for Webbrowsing, a data rate of at least 56 kilobits per second (kbps) orhigher is required.

[0005] In addition, the very nature of the data traffic itself isdifferent from the nature of voice communication. Voice requires acontinuous duplex connection; that is, the user at one end of aconnection expects to be able to transmit and receive to the user at theother end of a connection continuously, while at the same time the userat the other end is also able to transmit and receive. However, accessto Web pages over the Internet is, in general, very burst oriented.Typically, the user of a remote client computer specifies the address ofcomputer files such as on a Web server. This request is then formattedas a relatively short data message, typically less than a 1000 bytes inlength. The other end of the connection, such as at a Web server in thenetwork, then replies with the requested data file which may be from 10kilobytes to several megabytes of text, image, audio, or video data.Because of delays inherent in the Internet itself, users often expectdelays of at least several seconds or more before the requested contentbegins to be delivered to them. And then once that content is delivered,the user may spend several seconds or even minutes reviewing, readingthe contents of the page before specifying the next page to bedownloaded.

[0006] Furthermore, voice networks were built to support high mobilityusage; that is, extreme lengths were taken to support highway speed typemobility to maintain connections as the users of voice based cellularand PCS networks travel at high speeds along a highway. However, thetypical user of a laptop computer is relatively stationary, such assitting at a desk. Thus, the cell-to-cell high speed mobility consideredcritical for wireless voice networks is typically not required forsupporting data access.

SUMMARY OF THE INVENTION

[0007] It would make sense to retrofit certain components of theexisting wireless infrastructure to more efficiently accommodatewireless data. The additional functionality implemented for a new classof users who are high data rate but low mobility users should bebackwards compatible with existing functionality for users who are lowdata rate, high mobility. This would permit using the same frequencyallocation plans, base station antenna, build out sites, and otheraspects of the existing voice network infrastructure to be used toprovide the new high speed data service.

[0008] It would be particularly important to support as high a data rateas possible on the reverse link of such a network that is carrying dataon the reverse link, e.g., from the remote unit to the base station.Consider that existing digital cellular standards such as the IS-95 CodeDivision Multiple Access (CDMA) specify the use of different codesequences in a forward link direction in order to maintain minimuminterference between channels. Specifically, such a system employsorthogonal codes on the forward link, which defines individual logicalchannels. However, the optimum operation of such a system requires allsuch codes to be time aligned to a specific boundary to maintainorthogonality at the receiver. Therefore, the transmissions must besynchronized.

[0009] This is not a particular concern in a forward link directionsince all transmissions originate at the same location, i.e., at a basetransceiver station location. However, currently, digital cellular CDMAstandards do not attempt to use or require orthogonality betweenchannels in a reverse link direction. It is generally assumed that it istoo difficult to synchronize transmissions originating from remote unitslocated in different locations and at potentially quite differentdistances from the base station. Instead, these systems typically use achip level scrambling code with unique shifts of this long pseudorandomcode to distinguish the individual reverse link channels. Use of thisscrambling, however, thus precludes the possibility of different users'transmissions being orthogonal to one another.

[0010] Accordingly, one embodiment of the present invention includes asystem that supports communication among members of a first group ofusers and a second group of users. The first group of users, which maybe legacy users of a digital Code Division Multiple Access (CDMA)cellular telephone system, encode their transmissions with a commonfirst code. Such first group of users are uniquely identifiable byproviding a unique code phase offset for each user. The second group ofusers, who may be users of a high speed data service, encode theirtransmissions using the same code and one of the code phase offsets ofthat code. However, each of the users of the second group further encodetheir transmissions with an additional code, the additional code beingunique for each of the users of the second group. This permits thetransmissions of the second group of users to be orthogonal to eachother while still maintaining the appearance of collectively being asingle user of the first group.

[0011] The code assigned to the first group of users may be a commonchipping rate, pseudorandom code. The code assigned to the second groupof terminals may typically be a set of unique orthogonal codes. Theindividual members of the first group of terminals may be distinguishedby scrambling codes that have unique phase offsets of a selected longerpseudorandom noise sequence.

[0012] In a preferred embodiment, certain steps are taken to ensureproper operation of the signaling among the second group of users orso-called “heartbeat.” Specifically, a common code channel may bededicated for use as a synchronization channel. This permits themaintenance of proper timing of the transmissions of the second group ofterminals if, for example, the coding scheme is implemented in a reverselink direction.

[0013] In another embodiment, the users of the second group may beallocated specific time slots in which to transmit and thereforemaintain the orthogonality through the use of time division multipleaccess. Again, the point is that the users of the second groupcollectively appear as a single user to the transmissions of the usersin the first group.

[0014] The principles of the present invention allow current CDMAsystems, designed for vehicular mobility, to support soft handoff fororthogonal channel users on their reverse link to increase therobustness of reverse link channel connections in a highly variable RFenvironment.

[0015] Since an orthogonal link must be time aligned to maintainorthogonality from one user to the next, a timing control loop isemployed from a single base station. Orthogonality is not easilyachieved to two base stations in a reverse link direction because therelative propagation time delays complicate time alignment at both basestations. Therefore, to use an orthogonal reverse link with softhandoff, there is a primary reverse link base station providing timingcontrol and secondary base station(s) that may receive the transmissionsnon-orthogonally.

[0016] Specific criteria are defined to determine when it isadvantageous to reassign the timing control from the primary basestation to the secondary base station allowing for change of theorthogonal link from the first to the second base station. While thereis only one orthogonal base station, signal levels received at thesecond base station may be sufficient for reception. These signals maybe used to provide for diversity. This is particularly useful in highmobility systems.

[0017] Although only a single base station performs timing control, in apreferred embodiment, both perform power control. This is because, asthe path loss to the non-orthogonal base station decreases as the usermoves, the received power may become so strong it begins to generateexcessive interference, reducing the capacity of the secondary basestation. Therefore, when the signal level is adequate for reception atthe secondary base station, commands or messages are transmitted to thesubscriber unit to reduce the transmitted power. While these commandsaffect the received power at both the orthogonal base station and thenon-orthogonal base station, it may be appropriate to reassign thetiming control from the primary base station to the secondary basestation. A typical condition may be when the measured path loss to thenon-orthogonal or secondary base station exceeds some thresholddifference of, for instance, 10 db.

[0018] Existing CDMA systems define reverse-link channelizationsnon-orthogonally. This is performed by defining unique spreading codeshifts for each reverse-link user. Orthogonal and non-orthogonalbackward compatibility can be achieved by orthogonal users for a primarybase station sharing the same spreading code. When these user signalsare received at other base stations, it is unlikely that they will betime aligned, but they will all have unique code shifts and be able tobe uniquely identified based on the combination of code shift andorthogonal code. These signals are no more interfering than the standardnon-orthogonal signals that are legacy to existing CDMA systems.Therefore, just as soft handoff is performed today, it can be performedwith an orthogonal primary base station and non-orthogonal secondarybase stations.

[0019] When the primary base station is re-assigned such that the timingnow comes from a secondary base station (i.e., reverse link timingcontrol handoff has taken place), there may be a significant delay andcode phase offset. Using a conventional one-bit differential timingcontrol loop may be too slow to quickly obtain orthogonality with thenew base station when it is handed off. Therefore, when the handoffoccurs, a gross timing adjustment command or message may be used torapidly re-align the reverse link, where the gross timing adjustment maybe absolute or relative. In the case of the timing command, thesubscriber unit is told to make a coarse timing adjustment; in the caseof the timing message, the subscriber unit autonomously responds toinformation in the timing message.

[0020] The criteria for timing control hand-off may be based oncriteria, including at least one of the following:

[0021] 1. The metric of an alternative path exceeds a threshold for adesignated period of time;

[0022] 2. The metric of an alternative path exceeds a threshold relativeto the current path for a designated period of time;

[0023] 3. The currently selected path drops below an absolute metric; or

[0024] 4. The candidate path exceeds an absolute metric, where themetric may be one or more of the following

[0025] a. Power;

[0026] b. SNR;

[0027] c. Variance of the power;

[0028] d. Variance of the SNR; or

[0029] e. Relative ratio of the above metrics between the two paths(i.e., the orthogonal link and the non-orthogonal link).

[0030] Power control (or SNR control) of an orthogonal reverse link (RL)may be based on both orthogonal (aligned) and non-orthogonal paths. Whenthe SNR of a non-orthogonal path meets a quality criterion as listedabove while a power control loop is active, timing control of thesubscriber unit may be re-assigned to the base station associated withthe non-orthogonal path.

[0031] Referring to the power control loop, if a command is sent, ratherthan a message or report, the command may be the minimum of the SNR ofeach path. For example, if two paths are being tracked, and one needspower and the other has too much power, the power is commanded to belessened. This applies to a soft hand-off function as well, where thepower output by the subscriber unit is increased only if all commands ormessages providing power metrics require it to be increased.

[0032] There may be a relative offset between commands from anon-orthogonal path of a base station and those of the orthogonal path.For instance, the commands requiring more or less power fromnon-orthogonal paths may need to be more consistent or for a longerperiod of time or for a longer duration before the orthogonal path isignored and the other paths control the reduction in power. The intrabase station orthogonal zone may be handled in a like manner, as above.

[0033] Power control may be maintained by both orthogonal andnon-orthogonal base stations while timing orthogonality is controlled byone base station. While power control is being maintained to both theorthogonal and non-orthogonal base stations, commands or messagesincluding metrics must be sent to the subscriber unit transmitter downthe forward link.

[0034] The power control commands from each base station may be basedupon whether a quality metric is achieved at each respective basestation. This quality metric may be bit error rate, signal-to-noiseratio, received power, or Ec/Io. Provided the metric is satisfied, thena command to reduce transmission power is sent. Since the accessterminal receives commands from both base stations, often it willreceive conflicting commands. When this occurs, the access terminalobeys the command to power down if one exists. This is effectively anexclusive-OR function; for instance, a power-up occurs only if both basestations command power up. If either base station commands a power-down,then a power-down occurs at the access terminal. This holds true formulti-bit commands as well, where the minimum increase or the maximumdecrease in power is obeyed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The foregoing and other objects, features and advantages of theinvention will be apparent from the following more particulardescription of preferred embodiments of the invention, as illustrated inthe accompanying drawings in which like reference characters refer tothe same parts throughout the different views. The drawings are notnecessarily to scale, emphasis instead being placed upon illustratingthe principles of the invention.

[0036]FIG. 1 is a block diagram of a wireless communications systemsupporting orthogonal and non-orthogonal links;

[0037]FIG. 2 is a block diagram of a circuit employed by the accessterminal of FIG. 1;

[0038]FIG. 3 is a block diagram of the circuit of FIG. 2 furtherincluding a code generator to operate on an orthogonal link with otheraccess terminals;

[0039]FIG. 4 is a block diagram of the wireless communications system ofFIG. 1 having multiple field units using orthogonal and non-orthogonallinks;

[0040]FIG. 5 is a block diagram of a base station processor (BSP) ofFIG. 4 having an orthogonal timing controller to control the timing ofaccess terminals on the orthogonal link;

[0041]FIG. 6A is a network diagram of the network of FIG. 4 having analignment controller located in the base station processors;

[0042]FIG. 6B is a network diagram of the network of FIG. 4 having analignment controller located in the field unit;

[0043]FIG. 6C is a network diagram of the network of FIG. 4 having analignment controller located in a base station controller;

[0044]FIG. 7 is a flow diagram of processes that may be employed by thebase terminal station and access terminals of FIG. 4 to make signalsmutually orthogonal;

[0045]FIG. 8 is a flow diagram of processes that may be employed by thebase terminal stations and access terminal in the multi-cell environmentof FIG. 4 for soft-handoff; and

[0046]FIG. 9 is a flow diagram of processes that may be employed by thebase terminal stations and access terminals of FIG. 1 for power control.

DETAILED DESCRIPTION OF THE INVENTION

[0047] A description of preferred embodiments of the invention follows.

[0048]FIG. 1 is a block diagram of a Code Division Multiple Access(CDMA) communications system 10 that makes use of a signal encodingscheme in which a first class of logical channels are assigned uniquelong codes with different code phase offsets, and a second class oflogical channels are provided by using a common code and common codephase offset, combined with an additional coding process using a uniqueorthogonal code for each channel.

[0049] In the following detailed description of a preferred embodiment,the communications system 10 is described such that the shared channelresource is a wireless or radio channel. However, it should beunderstood that the techniques described here can be applied toimplement shared access to other types of media such as telephoneconnections, computer network connections, cable connections, and otherphysical media to which access is granted on a demand driven basis.

[0050] The system 10 supports wireless communication for a first groupof users 110 as well as a second group of users 210. The first group ofusers 110 are typically legacy users of cellular telephone equipmentsuch as wireless handsets 113-1, 113-2, and/or cellular mobiletelephones 113-h installed in vehicles. This first group of users 110principally use the network in a voice mode whereby their communicationsare encoded as continuous transmissions. In a preferred embodiment,these users' transmissions are forwarded from the subscriber units 113through forward link 40 radio channels and reverse link 50 radiochannels. Their signals are managed at a central location that includesa base station antenna 118, base transceiver station (BTS) 120, basestation controller (BSC) 123. The first group of users 110 are thereforetypically engaged in voice conversations using the mobile subscriberunits 113, BTS 120, and BSC 123 to connect telephone connections throughthe Public Switch Telephone Network (PSTN) 124.

[0051] The forward link 40 in use by the first group of users may beencoded according to well known digital cellular standards such as thisCode Division Multiple Access (CDMA) standard defined in IS-95Bspecified by the Telecommunications Industry Association (TIA). Thisforward link 40 includes at least a paging channel 141 and trafficchannel 142, as well as other logical channels 144. These forward link40 legacy channels 141, 142, 144 are defined in such a system by usingorthogonally coded channels. These first group of users 110 also encodetheir transmissions over the reverse link 50 in accordance with theIS-95B standard. They therefore make use of several logical channels ina reverse link 50 direction, including an access channel 151, trafficchannel 152, and other logical channels 154. In this reverse link 50,the first group of users 110 typically encode the signals with a commonlong code using different code phase offsets. The manner of encodingsignals for the legacy users 110 on the reverse link 50 is also wellknown in the art.

[0052] The communications system 10 also includes a second group ofusers 210. This second group of users 210 are typically users whorequire high speed wireless data services. Their system componentsinclude a number of remotely located Personal Computer (PC) devices212-1, 212-2, . . . 212-h, . . . 212-l, corresponding remote SubscriberAccess Units (SAUs) 214-1, 214-2, . . . 214-h, . . . 214-l, andassociated antennas 216-1, 216-2, . . . 216-h, . . . 216-l. Centrallylocated equipment includes a base station antenna 218, and a BaseStation Processor (BSP) 220. The BSP 220 provides connections to an froman Internet gateway 222, which in turn provides access to a data networksuch as the Internet 224, and network file server 230 connected to thenetwork 222.

[0053] The PCs 212 may transmit data to and receive data from networkserver 230 through bi-directional wireless connections implemented overthe forward link 40 and reverse link 50 used by the legacy users 110. Itshould be understood that in a point to multi-point multiple accesswireless communication system 10 as shown, a given base stationprocessor 220 supports communication with a number of different activesubscriber access units 214 in a manner which is similar to a cellulartelephone communication network.

[0054] In the present scenario, the radio frequencies allocated for useby the first group 110 are the same as those allocated for use by thesecond group 210. The present invention is specifically concerned withhow to permit a different encoding structure to be used by the secondgroup 210 while creating minimal interference to the first group 110.

[0055] The PCs 212 are typically laptop computers 212-l, handheld units212-h, Internet-enabled cellular telephones or Personal DigitalAssistant (PDA) type computing devices. The PCs 212 are each connectedto a respective SAU 214 through a suitable wired connection such as anEthernet-type connection.

[0056] An SAU 214 permits its associated PC 212 to be connected to thenetwork file server 230 through the BSP 220, gateway 222 and network224. In the reverse link direction, that is, for data traffic travelingfrom the PC 212 towards the server 230, the PC 212 provides an InternetProtocol (IP) level packet to the SAU 214. The SAU 214 then encapsulatesthe wired framing (i.e., Ethernet framing) with appropriate wirelessconnection framing and encoding. The appropriately formatted wirelessdata packet then travels over one of the radio channels that comprisethe reverse link 50 through the antennas 216 and 218. At the centralbase station location, the BSP 220 then extracts the radio link framing,reformatting the packet in IP form and forwards it through the Internetgateway 222. The packet is then routed through any number and/or anytype of TCP/IP networks, such as the Internet 224, to its ultimatedestination, such as the network file server 230.

[0057] Data may also be transmitted from the network file server 230 tothe PCs 212 in a forward link 40 direction. In this instance, anInternet Protocol (IP) packet originating at the file server 230 travelsthrough the Internet 224 through the Internet gateway 222 arriving atthe BSP 220. Appropriate wireless protocol framing and encoding is thenadded to the IP packet. The packet then travels through the antenna 218and 216 to the intended receiver SAU 214. The receiving SAU 214 decodesthe wireless packet formatting, and forwards the packet to the intendedPC 212 which performs the IP layer processing.

[0058] A given PC 212 and the file server 230 can therefore be viewed asthe end points of a duplex connection at the IP level. Once a connectionis established, a user at the PC 212 may therefore transmit data to andreceive data from the file server 230.

[0059] From the perspective of the second group of users 210, thereverse link 50 actually consists of a number of different types oflogical and/or physical radio channels including an access channel 251,multiple traffic channels 252-1, . . . 252-t, and a maintenance channel53. The reverse link access channel 251 is used by the SAUs 240 to sendmessages to the BSP 220 to request that traffic channels be granted tothem. The assigned traffic channels 252 then carry payload data from theSAU 214 to the BSP 220. It should be understood that a given IP layerconnection may actually have more than one traffic channel 252 assignedto it. In addition, a maintenance channel 253 may carry information suchas synchronization and power control messages to further supporttransmission of information over the reverse link 50.

[0060] Similarly, the second group of users have a forward link 40 thatincludes a paging channel 241, multiple traffic channels 242-1 . . .242-t, and maintenance channel 243. The paging channel 241 is used bythe BSP 220 to not only inform the SAU 214 that forward link trafficchannels 252 have been allocated to it, but also to inform the SAU 214of allocated traffic channels 252 in the reverse link direction. Trafficchannels 242-1 . . . 242-t on the forward link 40 are then used to carrypayload data information from the BSP 220 to the SAUs 214. Additionally,maintenance channels 243 carry synchronization and power controlinformation on the forward link 40 from the base station processor 220to the SAUs 214. It should be understood that there are typically manymore traffic channels 241 than paging channels 241 or maintenancechannels 243. In the preferred embodiment, the logical forward linkchannels 241, 242, and 243 and 251, 252, and 253 are defined byassigning each channel a pseudorandom noise (PN) channel code. Thesystem 10 is therefore a so-called Code Division Multiple Access (CDMA)system in which multiple coded channels may use the same radio frequency(RF) channel. The logical or codes channels may also be further dividedor assigned among multiple active SAUs 214.

[0061] The sequence of signal processing operations is typicallyperformed to encode the respective reverse link 50 logical channels 51,52, and 53. In the reverse link direction, the transmitter is one of theSAUs 214 and the receiver is the Base Station Processor (BSP) 220. Thepreferred embodiment of the invention is implemented in an environmentwhere legacy users of a CDMA digital cellular telephone system such asone operating in accordance with the IS-95B standard are also present onthe reverse link 50. In an IS-95B system, reverse link CDMA channelsignals are identified by assigning non-orthogonal pseudorandom noise(PN) codes.

[0062] Turning attention now to FIG. 2, the channel encoding process forthe first group of legacy users 110 will be described in greater detail.This first class of users includes, for example, digital CDMA cellulartelephone system users that encode signals according to the IS-95Bstandard as mentioned above. The individual channels are thereforeidentified by modulating the input digitized voice signal by apseudorandom noise (PN) code sequence for each channel. Specifically,the channel encoding process takes an input digital signal 302 thatrepresents the information to be transmitted. A quadrature modulator 304provides an in-phase (i) and quadrature (q) signal path to a pair ofmultipliers 306-i and 306-q. A short pseudorandom noise (PN) codegenerator 305 provides a short (in this case a 2 15 -1 or 32767 bit)length code used for spectrum spreading purposes. The short codetypically therefore is the same code for each of the logical channelsfor the first group 110.

[0063] A second code modulation step is applied to the (i) and (q)signal paths by multiplying the two signal paths with an additional longPN code. This is accomplished by the long code generator 307 and thelong code multipliers 308-i and 308-q. The long code serves to uniquelyidentify each user on the reverse link 50. The long code may be a verylong code, which, for example, only repeats every 2 42 -1 bits. The longcode is applied at the short code chipping rate, e.g., one bit of thelong code is applied to each bit output by the short code modulationprocess, so that further spectrum spreading does not occur.

[0064] Individual users are identified by applying different phaseoffsets of the PN long code to each user.

[0065] It should be understood that other synchronization steps need notbe taken for the first group of users 110. Specifically, thesetransmissions on the reverse link 50 are designed to be asynchronous andtherefore are not necessarily perfectly orthogonal.

[0066]FIG. 3 is a more detailed view of the channel encoding process forthe second group of users 210. This second group 210, for example,includes wireless data users that encode signals according to a formatoptimized for data transmission.

[0067] The individual channels are identified by modulating the inputdata by a pseudorandom noise (PN) code sequence that is the same codesequence used for the first group of users 110. However, as will beunderstood shortly, the channels in the second group 210 are uniquelyidentified by specific orthogonal codes such as Walsh codes.Specifically, the channel encoding process for this second group ofusers 210 takes an input digital signal 402 and applies a number ofcodes as generated by a short code generator 405, Walsh code generator413, and long code generator 407.

[0068] As a first step, a quadrature modulator 404 provides an in-phase(i) and quadrature (q) signal path to a first pair of multipliers 406-iand 406-q. The short pseudorandom noise (PN) code generator 405 providesa short, in this case, a 215 length code used for spectrum spreadingpurposes. This short code therefore is the same as the short PN codeused for each of the channels in the first group 110.

[0069] A second step in the process is to apply an orthogonal code suchas generated by the Walsh code generator 413. This is accomplished bythe multipliers 412-i and 412-q impressing the orthogonal code on eachof the in-phase and quadrature signal paths. The orthogonal codeassigned to each logical channel is different, and uniquely identifiessuch channels.

[0070] In a final step of the process, a second pseudorandom noise (PN)long code is applied to the (i) and (q) signal paths. The long codegenerator 407 thus forwards the long code to a respective one of thein-phase 408-i and quadrature 408-q multipliers. This long code does notuniquely identify each user in the second group 210. Specifically, thiscode may be one of the very same long codes that are used in the firstgroup that uniquely identify their first group of users 110. Thus, forexample, it is applied in the same manner as a short code chipping ratecode so that one bit of the long code is applied to each bit output bythe short code modulation process. In this manner, all of the users inthe second group 210 appears as a single legacy user of the first group110. However, the users of the second group 210 may be uniquelyidentified given that they have been assigned unique orthogonal Walshcodes.

[0071] As the implementation in the preferred embodiment is on a reverselink 50, additional information must be provided in order to maintainorthogonality among the various users in the second group 210.Specifically, a maintenance channel 243 is therefore included in theforward link 40. This maintenance or “heartbeat” channel providessynchronization information and/or other timing signals so that theremote units 214 may synchronize their transmissions appropriately. Themaintenance channel may be time slotted. For more details of theformatting of this forward link maintenance channel 243, reference canbe made to a co-pending U.S. Patent application Ser. No. 09/775,305filed Feb. 1, 2001 entitled “MAINTENANCE LINK USING ACTIVE/STANDBYREQUEST CHANNELS,” which is hereby incorporated by reference in itsentirety.

[0072] It should be understood that certain infrastructure may thereforebe shared by both the second group of users 210 and first group of users110. For example, the antennas 218 and 118 although shown as separatebase station antennas in FIG. 1 may indeed be a shared antenna.Likewise, the location for the antennas may therefore be the same. Thispermits the second group of users 210 to share equipment and physicalbuild-out locations already in place and in use by the legacy users 110.This greatly simplifies the deployment of wireless infrastructure forthis new group of users 210, for example, new locations and new antennasites need not be built out.

[0073]FIG. 4 is a network diagram similar to FIG. 1. In this wirelessnetwork 400, a first Base Station Processor (BSP) 220-1 and second basestation processor 220-2 (collectively 220) provide access to othernetworks (e.g., the Internet or PSTN) for access terminals 213-1, 213-2,. . . , 213-3 and handheld units 113-1, 113-2, and 113-3. The basestation processors 220 also support soft handoff of CDMA reverse linksusing orthogonal channels for non-legacy access terminals 213 while atthe same time allowing legacy handheld units 113 to use reverse links ina typical manner. Access terminals 213 and handheld units 113 areinterchangeably referred to as field units or Subscriber Access Units(SAUs).

[0074] “Legacy” field units refers to field units that are not equippedwith a modulation process that applies unique orthogonal codes forsharing a common reverse link channel with other field units.“Non-legacy” field units refers to field units that are equipped with amodulation process that applies unique orthogonal codes for sharing acommon reverse link channel with other field units. The BSPs 220 supportsoft handoff by selectively re-assigning timing control of reverse linkchannels based on criteria. In a preferred embodiment, both BSPs 220provide power control feedback to the field units.

[0075] Continuing to refer to FIG. 4, above the antenna towers 218 arefirst and second timing diagrams 403-1 and 403-2 (collectively 403) thatillustrate the related timings of reverse link signals for each of thefield units communicating with the respective base station processors220. These timing diagrams 403 illustrate a distinction betweenorthogonal reverse link channels that are time aligned and orthogonal ornon-orthogonal channels that are not time aligned. As discussed above,each non-legacy access terminals 213 that shares a common reverse linkchannel has an additional coding process to add a unique orthogonal codeto distinguish its reverse link signals from reverse link signals ofother network devices using the common reverse link channel.

[0076] For purposes of this discussion, it is assumed that (i) theaccess terminals 213 share a common reverse link orthogonal channel and(ii) the three handheld units 113 use legacy, non-orthogonal,communication techniques in the reverse link.

[0077] In the first timing diagram 403-1, the first base stationprocessor 220-1 employs an alignment controller (not shown) to align thetiming of reverse link orthogonal channels of access terminals for whichthe BSP 220-1 controls. In this case, the BSP 220-1 controls the timingof the reverse link logical channels 420-1 and 420-2, represented byvertical tick marks 425-1 and 425-2, of the first and second field units213-1 and 213-2, respectively. Reverse link channels that have theirreverse links time aligned (i.e., common long codes phase aligned) arereferred to as “native” orthogonal channels 410. The third accessterminal 213-3 that is also in communication with the first base stationprocessor 220-1 does not have its reverse link logical channel 420-3(425-3) time aligned with the reverse link logical channels of the firstand second access terminals 213-1 and 213-2. The third access terminal213-3 has its reverse link channel 420-3 controlled by the second BSP220-2. Accordingly, the timing of the reverse link logical channel 420-3(425-3) for the third field unit 213-3 is shown offset in the firsttiming diagram 403-1 from the native orthogonal channels 425-1 and425-2.

[0078] In the second timing diagram 403-2, reverse link logical channels420-1, 420-3, 420-4, 420-5, and 420-6 of the five wireless networkdevices 213-1, 213-3, 113-1, 113-2, and 113-3 in communication with thesecond base station processor 220-2 are represented by vertical tickmarks 425-1, 425-3, 425-4, 425-5, and 425-6, respectively. The secondBSP 220-2 controls the timing of the third access terminal 213-3 reverseorthogonal link 420-3 (425-3) but neither of the other access terminals213-1, 213-2. Therefore, as expected, the reverse link logical channels420 (425) are offset in phase from one another at the second BSP 220-2,as indicted in the second timing diagram 403-2. Three of the reverselink channels 425-1, 425-5, and 425-6 are relatively close together intime at the second BSP 220-2 and are referred to as “foreign” orthogonalchannels 415.

[0079] The foreign orthogonal channels 415 are not truly orthogonal inthat the channels do not have the unique orthogonal codes to distinguishone from another on a common, reverse link channel. Therefore, if theforeign orthogonal channels 415 were to be aligned, they woulddestructively interfere with each other at the second BSP 220-2. In aparticular situation, each of the base station processors 220 may besupporting native orthogonal channels 410 and foreign or non-orthogonalchannels 415. This situation indicates that a combination of non-legacyand legacy field units, respectively, can be used within the same cellzone.

[0080] In existing orthogonal technology, there is no soft handofftechnique in the reverse link for when a field unit, such as one of theaccess terminals (e.g., 213-3), moves from a cell zone of a first basestation processor 220-1 to a cell zone of a second base stationprocessor 220-2. The reverse link soft handoff technique disclosedherein (i) supports communication in the reverse link from non-legacywireless network devices 213 to multiple base station processors 220,(ii) performs timing and power control (described later), and (iii)coordinates which of the multiple base station processors 220 is the“master” of the reverse link timing control for a field unit based oncriteria, described in reference to FIG. 8. By coordinating which of themultiple BSPs 220 controls timing of the reverse link channel of a givenaccess terminal 213, the given access terminal 213 can move from onecell zone to another cell zone without loss of connection in the reverselink. The principles of the present invention also include a techniquefor rapid orthogonal timing alignment (i.e., adjusting the phase of thelong code of the common logical channel for an access terminal 213 suchthat the common reverse link channel is time aligned, or mutuallyorthogonal, with the common reverse link channel of other accessterminals 213).

[0081] The base station processor 220 receiving control of the timing ofthe reverse link channel determines a gross offset of the timing of thefield unit's reverse link logical channel as a function of the timing ofthe reverse link logical channel of other field units sharing the samereverse link logical channel. The gross offset is transmitted to thefield unit 213 in the form of an offset command or offset message. Basedon the gross offset information, the field unit makes a coarse timingadjustment of the logical channel in accordance with the gross timingoffset. Following the coarse timing adjustment, a fine timing adjustmentmay be made in accordance with fine timing offsets that may be measuredby the base station processor 220 following the coarse timing adjustmentof the reverse link logical channel 420.

[0082]FIG. 5 is a block diagram of one of the base station processors220-1 that includes provisions for soft handoff of a CDMA reverse linkutilizing an orthogonal channel structure. The base station processor220-1 receives reverse link channels from the field units 113, 213 viathe antenna tower 218. A receiver 505 receiving a reverse link channelfrom a given field unit 213 sends the received signal to an orthogonaltiming controller 510. The orthogonal timing controller 510, orequivalent unit, determines a gross timing offset 513 with respect toreverse link channels from other field units sharing the same reverselink logical channel. The gross timing offset 513 may be an absolutemeasure for transmittal to the given field unit 213 in the form of acommand or may be a relative measure and sent back to the given fieldunit 213 in the form of a message, with the given field unit 213 usingadditional processing to determine the timing offset (i.e., phaseadjustment) of the reverse link signal. A combination of absolute andrelative measures may also be employed.

[0083]FIG. 6A is a schematic diagram of the network having the firstbase station processor 220-1 and second base station processor 220-2.The base station processors 220 include respective alignment controllers515. The alignment controllers 515 are used by the base stationprocessors 220 to select or control which base station processor 220controls the timing alignment of the reverse links 420 of the fieldunits 213.

[0084] To determine which BSP 220 should control the timing alignmentfor the field unit 213-1, the alignment controllers 515 may calculate ametric (e.g., Signal-to-Noise ratio (SNR)) associated with the signalreceived from the field unit 213-1.

[0085] A given alignment controller 515 may issue a message to otheralignment controller(s) 515 to tell the other base station processors220 that the associated base station processor 220 associated with thegiven alignment controller 515 is going to control the timing of thereverse link channel of the field unit 213-1. Alternatively, the givenalignment controller 515 may issue a command or message to anotheralignment controller 515, such as the alignment controller 515 in thesecond base station processor 220-2, that the second base stationprocessor 220-2 should control the timing of the reverse link channel ofthe field unit 213-1. Other negotiating arrangements may occur betweenor among the alignment controllers 515 to determine which base stationprocessor 220 is going to control the alignment of the field unit 213.Once a base station processor 220 has been commanded or has elected tocontrol the timing of the orthogonal reverse link channel, theorthogonal timing controllers 510 are employed to determine a grosstiming offset, as discussed above for facilitating the timing controlhandoff.

[0086]FIG. 6B is a schematic diagram of the wireless network in whichthe alignment controller 515 is deployed as part of the field unit213-1, in this case incorporated into the subscriber access unit 214-1.Alternatively, the alignment controller 515 may be included in the PC212-1 or as a standalone unit electrically connected to either theSubscriber Access Unit (SAU) 214-1 or PC 212-1.

[0087] In this arrangement, the alignment controller 515 provides acommand or message to the SAU 214-1 at the field unit 213-1 to cause thefield unit 213-1 to respond to a timing control signal received fromeither the first base station processor 220-1 or second base stationprocessor 220-2.

[0088]FIG. 6C is a schematic diagram of the wireless network 400 inwhich the alignment controller 515 is deployed in the base stationcontroller (123). In this case, the alignment controller 515 may receiveinformation from each of the orthogonal timing controllers 510 from thefirst base station 220-1 or the second base station 220-2 to determinewhich base station processor 220 should be controlling the timing of theorthogonal, reverse link channel for the field unit 213-1. The alignmentcontroller 515 may make this determination based on a number of factors,such as the signal-to-noise ratio of the reverse link signal at each ofthe base station processors 220. The alignment controller 515 may usecommands or messages to indicate which base station processor 220 is tocontrol the timing of the reverse link of the field unit 213-1. Ineither case, the selected base station processor 220 may issue a commandor message to the field unit 213-1 that it is the base station processor220 that will be controlling the timing of the orthogonal reverse linkchannel. It should be understood that the alignment controller 515 mayalso understand the concept of diversity and make selections as to whichbase station processor 220 is to control the timing of the reverse linkchannel so as to maximize the effectiveness of diversity between thebase station processors 220.

[0089]FIG. 7 is a flow diagram of a soft handoff process of a CDMAorthogonal reverse link in accordance with the principles of the presentinvention. In this example, the first base station processor 220-1executes a first process 700, and the access terminal 213 executes asecond process 735. Following the start of the BSP process 700 in step705, the BSP process 700 waits to receive a reverse link signal in step710 from the access terminal 213. Following the start of the accessterminal process 735 in step 740, the access terminal 213, in step 745,transmits a reverse link signal with the unique orthogonal code on areverse link channel common to reverse link signals of other accessterminals 213. The BSP process 700 receives the reverse link signal instep 710 and continues in step 715. In step 715, the BSP process 700determines whether the long code, identifying the access terminal 213belonging to an orthogonal reverse link group, in the reverse linksignal is in phase with long codes of other access terminals 213 in thesame access terminal group, as described in reference to FIGS. 2 and 3.It is the long codes, and not the unique, specific, orthogonal codes,such as Walsh codes, that are time aligned by the base station processor700. The unique, identifying codes of the reverse link signals aremutually orthogonal when the long codes are phase.

[0090] If the long code in the reverse link signal is in phase (i.e.,time aligned) with the long codes of other reverse link signals of otheraccess terminals 213 in the same mutually orthogonal reverse link group,the process 700 ends at step 730. If the long code is not in phase withlong codes in reverse link signals of other access terminals, the BSPprocess 700 continues in step 720, where a determination of the grosstiming offset is made by the orthogonal timing controller 510, asdiscussed above in reference to FIG. 5.

[0091] The BSP process 700 continues in step 725, where the base stationprocessor 220 transmits the gross timing offset to the access terminal213 in the form of a command or message. The access terminal process 735receives the gross timing offset and adjusts the timing of the reverselink signal in step 750. The access terminal process 735 ends in step755, and the BSP process 700 ends in step 730.

[0092]FIG. 8 is a flow diagram of the two base station processors 220-1and 220-2 as they interact with the access terminal 213. The first basebase station processor 220-1 executes a process 800 that controls thetiming of the reverse link of the access terminal 213. The other basestation processor 220-2 executes a process 802 that provides processingthat is not controlling the timing of the reverse link of the accessterminal 213. The access terminal 213 executes its own process 833. Theprocess 833 is capable of receiving feedback, making adjustments to thetiming of the reverse link signal in coarse and fine amounts, and makingpower level adjustments in accordance with power level feedback receivedfrom the base station processors 220.

[0093] The access terminal 213 transmits signals (step 836) that arereceived by the first base station processor 220-1 and the second basestation processor 220-2. In this example, it is assumed that the firstbase station processor 220-1 has previously been selected to control thetiming of the reverse link signal by the access terminal 213. The firstbase station processor 220-1 thus receives the reverse link orthogonalsignals (step 803) from the access terminal 213 that is either alignedwith other reverse link signals sharing the same reverse link channel oris to be aligned with other reverse link signals from other accessterminals 213 using the same reverse link channel. The base stationprocessor 220-1 determines whether the signal from the access terminal213 meets a timing criterion or criteria in step 806. If the signal doesnot meet a timing criterion or criteria, the process 800 determines agross timing offset to feed back to the access terminal 213 to bring thesignal in alignment with the other signals using the same code. Feedbackis received by the access terminal 213 in step 839. If the signal meetsthe timing criterion or criteria, the process 800 continues in step 809,where the process 800 determines whether a fine timing offset isnecessary. If yes, the process 800 sends to the access terminal 213,which is the fine timing offset, which is received in step 839 of theprocess 833 executed by the access terminal 213. If no fine timingoffset is necessary, the process 800 continues in step 815.

[0094] In step 815, the base station processor 220-1 determines whetherthe power level of the signal transmitted by the access terminal 213should be adjusted. Similarly, the second base station processor 220-2also determines whether it should cause a power level adjustment in step815 of the access terminal 213. In either case, the power level offsetsare sent to the access terminal 213 in the forward link.

[0095] If no power level adjustment is needed, in reference to both thefirst base station processor process 800 and second base stationprocessor process 802, the respective processes continue to step 818,where a determination is made as to whether timing control handoffshould be initiated. Timing control handoff may be initiated based on aset of criteria:

[0096] (a) the metric of an alternative path exceeds a threshold for apredesignated period of time;

[0097] (b) the metric of an alternative path exceeds a thresholdrelative to the current path for a designated period of time;

[0098] (c) the currently selected path drops below an absolute metric;and

[0099] (d) the candidate path exceeds an absolute metric, where themetric may be one or more of the following:

[0100] (a) power;

[0101] (b) SNR;

[0102] (c) variance of the power;

[0103] (d) variance of the SNR; and

[0104] (e) relative ratio of the two paths.

[0105] If there has been an initiation of timing control handoff, then,in step 821, the base station processor 220-1 updates other base stationprocessors and the base station controller 123. The access terminal 213may also be told of the timing control handoff. If the timing controlhas not been handed off, the processes 800 and 802 continue in step 824,where a determination is made to release or accept the timing controlshould another base station processor 220, base station controller 123,or access terminal 213 send a command or message to the base stationprocessor 220 that it will be controlling the timing of the reverse linksignal. If the base station processor releases or accepts timing controlduties, the processes 800, 802 continue in step 830 to update systemoperating parameters; otherwise, the processes 800, 802 continue back tostep 803 to receive signals from the access terminals 213.

[0106] The process 833 executed by the access terminal 213 receivesfeedback in step 839 and processes the feedback as follows. First, if nofeedback is received, the process 833, in this embodiment, loops waitingfor feedback in step 839. If feedback is received, the process continuesin step 842 to determine whether a coarse timing adjustment command ormessage has been received. If yes, the coarse timing adjustment is madein step 845. It should be understood that the course timing adjustmentmay be an absolute or relative measure, as disclosed above.

[0107] In step 848, the access terminal 213 determines whether a finetiming adjustment command or message has been received. If yes, the finetiming adjustment is made in step 851. It should be understood that thefine timing adjustment is typically a differential command or message.Following the fine timing adjustment, the process 833 determines whethera power level adjustment command or message has been received. If yes,the access terminal 213 adjusts the power level in step 857.

[0108] Following the adjustments to the timing or power, the process 833updates the operating parameters of the access terminal 213 in step 860.Following update of the system parameters, the process 833 repeats atstep 839, awaiting feedback from one or more base station processors220.

[0109]FIG. 9 is a flow diagram of processes 900, 920 executed by thebase station processors 220 and the access terminal 213, respectively,for adjusting the power level of the reverse link signal transmitted bythe access terminal 213. Referring to the processes 900 executed by thebase station processors 220, the processes 900 begin in step 905. Instep 910, the base station processors 220 determine whether to cause theaccess terminal 213 to change the power level of the reverse link signalin step 910. If the change of the reverse link signal power level isdesired, feedback is sent to the access terminal 213 in the form of acommand or message. The base station processor 220 process 900 ends instep 915.

[0110] The process 920 executed by the access terminal 213 begins instep 925. Once feedback is received in step 930, the process 920continues in step 935, where a determination is made as to whether allbase station processors 220 are requesting a power level increase. Ifyes, the process 920 continues in step 940, where the access terminal213 increases the power level of the reverse link signal as much as thelowest increase feedback. If not all of the base station processors 220are requesting power level increase, a determination is made in step 945as to whether any base station processor 220 is requesting a power leveldecrease. If yes, the access terminal 213, in step 950, decreases apower level as much as a lowest decrease feedback. The process 920 endsin step 955 or may simply loop back to step 930 to wait to receive apower level feedback.

[0111] While power control is being maintained to both the orthogonaland non-orthogonal base stations, commands or metrics may be sent to thesubscriber base transmitter (i.e., access terminal 213) via a forwardlink. The power control commands from each base station processor 220may be based upon whether a signal quality metric is achieved at eachrespective base station processor 220. This signal quality metric may bea bit-error-rate (BER), signal-to-noise ratio (SNR), received power, orEc/Io, for example. Provided the metric is satisfied, a command toreduce transmission power may be sent. Since the access terminal 213receives commands or messages from both base station processors 220,often it reflects conflicting commands. When this occurs, the accessterminal 213 obeys the command to “power down.” This is effectively anexclusive-OR function; for instance, a “power up” occurs if both basestation processor 220 command power up. If either base station processor220 commands a power down, a power down occurs. This holds true formulti-bit commands as well, where the minimum increase or the maximumdecrease in power is obeyed.

[0112] While this invention has been particularly shown and describedwith references to preferred embodiments thereof, it will be understoodby those skilled in the art that various changes in form and details maybe made therein without departing from the scope of the inventionencompassed by the appended claims.

What is claimed is:
 1. A wireless communications system for aligningCode Division Multiple Access (CDMA) reverse link signals, the systemcomprising: a first base station having (i) a first receiver to receivea signal having a unique orthogonal code from a given subscriber unitover a first reverse link and (ii) a first timing controller coupled tothe receiver capable of determining a gross timing offset of the signalto make the signal essentially mutually orthogonal with signals from atleast one other subscriber unit on the first reverse link; a second basestation having (i) a second receiver to receive simultaneously thesignal having the unique orthogonal code from the given subscriber unitover a second reverse link and (ii) a second timing controller coupledto the second receiver capable of determining a gross timing offset ofthe signal to make the signal essentially mutually orthogonal withsignals from at least one other subscriber unit on the second reverselink; and an alignment controller in communication with the first andsecond timing controllers (i) to cause the signal to be orthogonallyaligned with the signals from said at least one other subscriber unit oneither the first reverse link or the second reverse link and (ii) toallow the signal to be orthogonally offset from the signals from said atleast one other subscriber unit on the other reverse link.
 2. Theapparatus according to claim 1 wherein, in response to being assignedresponsibility for orthogonal alignment, the first or second timingcontroller reports the timing offset to the given subscriber unit in theform of a timing command or timing message.
 3. The system according toclaim 1 wherein (i) the first base station includes a first powercontroller to determine a first power level of the coded signal at thefirst base station and (ii) the second base station includes a secondpower controller to determine a second power level of the coded signalat the second base station, wherein each power controller providesfeedback of the power level to the given subscriber unit in the form ofa power command or a power message.
 4. The system according to claim 3,wherein the power level feedback from the first and second powercontrollers causes the given subscriber unit to increase its power levelbased on the lesser of the two feedback signals and decrease its powerlevel based on the lesser of the two feedback signals.
 5. The systemaccording to claim 1 wherein the first base station includes thealignment controller and initiates timing control handoff.
 6. The systemaccording to claim 1 wherein the second base station includes thealignment controller and initiates timing control handoff.
 7. The systemaccording to claim 1 wherein the subscriber unit includes the alignmentcontroller and initiates timing control handoff.
 8. The system accordingto claim 1 wherein a base station controller coupled to the first andsecond base stations includes the alignment controller and initiatestiming control handoff.
 9. The system according to claim 1 wherein thealignment controller initiates timing control handoff, wherein thetiming control handoff is based on at least one of the followingcriteria: (a) a metric of the transmission path between the subscriberunit and the base station not controlling the timing exceeds a thresholdfor a predetermined timespan, (b) a metric of the transmission pathbetween the subscriber unit and the base station not controlling thetiming exceeds a threshold relative to a metric of a transmission pathbetween the base station controlling the timing and the subscriber unitfor a predetermined timespan, (c) a metric of the transmission pathbetween the base station controlling the timing and the subscriber unitdrops below an absolute metric, and (d) a metric of the transmissionpath between the base station not controlling the timing and thesubscriber unit exceeds an absolute metric.
 10. The system according toclaim 9 wherein the metric includes at least one of the following: (a)power, (b) signal-to-noise ratio (SNR), (c) variance of the power, (d)variance of the SNR, (e) between the orthogonally aligned path annon-orthogonally aligned paths between the given subscriber unit and thefirst and second base stations, relative ratio of the (i) power, (ii)SNR, (iii) variance of the power, or (iv) variance of the SNR, (f) biterror rate, and (g) energy per chip divided by the interference density(Ec/Io).
 11. In a wireless communications system, a method for aligningCode Division Multiple Access (CDMA) reverse link signals, the methodcomprising: by a first base station, (i) receiving a signal having aunique orthogonal code from a given subscriber unit over a first reverselink and (ii) determining a gross timing offset of the signal to makethe signal essentially mutually orthogonal with signals from at leastone other subscriber unit on the first reverse link; by a second basestation, (i) simultaneously receiving the signal having the uniqueorthogonal code from the given subscriber unit over a second reverselink and (ii) determining a gross timing offset of the signal to makethe signal essentially mutually orthogonal with signals from at leastone other subscriber unit on the second reverse link; and (i) causingthe signal to be orthogonally aligned with the signals from said atleast one other subscriber unit on either the first reverse link or thesecond reverse link and (ii) allowing the signal to be orthogonallyoffset from the signals from said at least one other subscriber unit onthe other reverse link.
 12. The method according to claim 11 wherein, inresponse to being assigned responsibility for orthogonal alignment, thefirst or second timing controller reports the timing offset to the givensubscriber unit in the form of a timing command or timing message. 13.The method according to claim 11 wherein (i) the first base stationincludes a first power controller to determine a first power level ofthe coded signal at the first base station and (ii) the second basestation includes a second power controller to determine a second powerlevel of the coded signal at the second base station, wherein each powercontroller provides feedback of the power level to the given subscriberunit in the form of a power command or a power message.
 14. The methodaccording to claim 13, wherein the power level feedback from the firstand second power controllers causes the given subscriber unit toincrease its power level based on the lesser of the two feedback signalsand decrease its power level based on the lesser of the two feedbacksignals.
 15. The method according to claim 11 wherein the first basestation includes the alignment controller and initiates timing controlhandoff.
 16. The method according to claim 11 wherein the second basestation includes the alignment controller and initiates timing controlhandoff.
 17. The method according to claim 11 wherein the subscriberunit includes the alignment controller and initiates timing controlhandoff.
 18. The method according to claim 11 wherein a base stationcontroller coupled to the first and second base stations includes thealignment controller and initiates timing control handoff.
 19. Themethod according to claim 11 wherein the alignment controller initiatestiming control handoff, wherein the timing control handoff is based onat least one of the following criteria: (a) a metric of the transmissionpath between the subscriber unit and the base station not controllingthe timing exceeds a threshold for a predetermined timespan, (b) ametric of the transmission path between the subscriber unit and the basestation not controlling the timing exceeds a threshold relative to ametric of a transmission path between the base station controlling thetiming and the subscriber unit for a predetermined timespan, (c) ametric of the transmission path between the base station controlling thetiming and the subscriber unit drops below an absolute metric, and (d) ametric of the transmission path between the base station not controllingthe timing and the subscriber unit exceeds an absolute metric.
 20. Themethod according to claim 19 wherein the metric includes at least one ofthe following: (a) power, (b) signal-to-noise ratio (SNR), (c) varianceof the power, (d) variance of the SNR, (e) between the orthogonallyaligned path an non-orthogonally aligned paths between the givensubscriber unit and the first and second base stations, relative ratioof the (i) power, (ii) SNR, (iii) variance of the power, or (iv)variance of the SNR, (f) bit error rate, and (g) energy per chip dividedby the interference density (Ec/Io).
 21. In a wireless communicationssystem, an apparatus for aligning Code Division Multiple Access (CDMA)reverse link signals, the apparatus comprising: at a first base station,(i) means for receiving a signal having a unique orthogonal code from agiven subscriber unit over a first reverse link and (ii) means fordetermining a gross timing offset of the signal to make the signalessentially mutually orthogonal with signals from at least one othersubscriber unit on the first reverse link; at a second base station, (i)means for simultaneously receiving the signal having the uniqueorthogonal code from the given subscriber unit over a second reverselink and (ii) means for determining a gross timing offset of the signalto make the signal essentially mutually orthogonal with signals from atleast one other subscriber unit on the second reverse link; and (i)means for causing the signal to be orthogonally aligned with the signalsfrom said at least one other subscriber unit on either the first reverselink or the second reverse link and (ii) means for allowing the signalto be orthogonally offset from the signals from said at least one othersubscriber unit on the other reverse link.
 22. A base station foraligning CDMA reverse link channels, the base station comprising: anorthogonal channel receiver to receive an orthogonally coded signal froma subscriber unit over a reverse link; and a timing controller to causecoarse timing adjustments to the timing of the coded signal in responseto a command or message to reassign timing control of the subscriberunit previously under timing control by another base station.
 23. In abase station, a method for aligning CDMA reverse link channels, themethod comprising: receiving an orthogonally coded reverse link signalfrom a subscriber unit over a reverse link; in response to a command ormessage to reassign timing control of the reverse link of a subscriberunit previously under timing control by another base station,determining a gross timing offset of the coded signal and causing acoarse timing adjustment to the timing of the reverse link coded signal.24. A base station for aligning a CDMA reverse link channel, the basestation comprising: means for receiving a unique, orthogonally codedreverse link signal from a subscriber unit over a reverse link; andmeans for determining a gross timing offset of the coded signal and forcausing coarse timing adjustments to the timing of the coded signal inresponse to a message to reassign timing control of the subscriber unitpreviously under timing control by another base station.
 25. Asubscriber unit operating in a wireless network aligning a CDMA reverselink channels, the subscriber unit comprising: an orthogonal channeltransmitter to transmit a unique, orthogonally coded signal over areverse link to a base station; and a timing adjustment unit to cause acoarse timing adjustment of the coded signal in response to receiving agross timing offset from the base station to make the coded signalessentially mutually orthogonal with coded signals from at least oneother subscriber unit on the reverse link with the base station.
 26. Ina subscriber unit operating in a wireless network, a method comprising:transmitting a unique, orthogonally coded signal over a reverse link toa base station; and making a coarse timing adjustment of the codedsignal in response to receiving a gross timing offset from the basestation to make the coded signal essentially mutually orthogonal withcoded signals from at least one other subscriber unit on the reverselink with the base station.
 27. A subscriber unit operating in awireless network, comprising: means for transmitting a unique,orthogonally coded signal over a reverse link to a base station; andmeans for making a coarse timing adjustment of the coded signal inresponse to receiving a gross timing offset from the base station tomake the coded signal essentially mutually orthogonal with coded signalsfrom at least one other subscriber unit on the reverse link with thebase station.
 28. In a system that supports Code Division MultipleAccess (CDMA) communications among members of a first group of terminalsand among members of a second group of terminals, a method comprising:assigning to the first group of terminals a first code, each user of thefirst group being uniquely identifiable by a unique code phase offset;assigning to the second group of terminals the same code as used by thefirst group but each user of the second group using a common phaseoffset of that code; assigning to each user of the second group anadditional code, the additional code being unique for each of theterminals of the second group; and for a given member of the secondgroup, determining a gross timing offset to align the given member withthe other members of the second group.
 29. A wireless communicationssystem comprising a first set of access units and a second set of accessunits, the first set of access units and the second set of access unitscapable of communicating with a central base station, the first set ofaccess units using a chip rate scrambling code to separate their userchannels, each individual unit of the first set of access units havingat least one unique, non-orthogonal scrambling sequence that is selectedfrom a unique time shift of a longer pseudo random noise sequence, andthe second group of access units (i) sharing a common chip ratescrambling code that is not used by the first group of access units and(ii) capable of making gross adjustments to the timing of the commonchip rate scrambling code.